Method of and apparatus for investing patterns under vacuum



c. H. BRA CE 2,274,186

METHOD OF AND APPARATUS FOR INVESTING PATTERNS UNDER VACUUM Feb. 24,1942.

Filed Dec. 9, 1940 1 3 m I Charles H'.Brace Gamma,

Patented F b. 24,1942

UNITED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR INVEST- INGPATTERNS UNDER VACUUM Charles Harold Brace; Minneapolis, Minn, assignorto General Refineries, Inc., Minneapolis,

Minn., a corporation of Minnesota Application December-9, 1940, SerialNo. 369,143

14 Claims. (01. 22-1131) My invention relates to methods of and moldingapparatus for investing patterns under vacuum, and has for'an object toprovide a method and apparatus whereby the molding can be quickly andefliciently performed.

Another object of the invention resides in pro ducing an apparatus bymeans of which standard flasks or casting rings may be employed.

A still furtherobject of the invention resides in applying to the upperend of a flask, a flask extension open at its ends and communicatingwith the interior of the flask and forming an ebullition chamber inwhich ebullition of the investment occurs during formation of the mold.A feature of the invention resides in providing a coupling. for.detachably connecting the flask extension to the flask. I

Another object of the invention resides in constructing said couplingwith two gripping portions adapted to extend about the flask and inconstructing said gripping portions of a resilient in subsequentlyremoving the base, coupling and A extension from the flask.

' within. suitable evacuating means.

friction material adapted to hold the flask and extension in properlyassembled relation.

Another object of'the invention resides in constructing the couplingwith a positioning flange forming seats for engagement with thejuxtaposed edges of the flask and flask extension for positioningthe'flasks with reference to the coupling and forming a seal between theflask and flask extension. 7

Another object of the invention resides in providing a base for closingthe lower end of the flask and supporting the pattern and forming asprue communicating with the mold cavity.

A still further object of the invention resides in constructing the basewith a gripping member formed of flexible resilient material for holdingthe base attached to the lower endof the flask.

An object of the rinvention resides in the method of investing patternsunder vacuum which consists in using an ordinary flask and in placingthe pattern within the flask and supportting the. same from the base, inapplying aooupling to the upper end of the flask, in inserting a flaskextension within said coupling, in placing the mold assembly within achamber and exhausting the air from within said chamber, and

Fig. 3 is a sectional view of the flask and base of the moldingapparatus with the coupling and flask extension removed. r

Fig. 4 is a View similar to Fig. 3 showing the completed mold.

My invention consists of a flask ID to which is attached a base H. Acoupling [2 is secured to the upper, end of the flask and'supports aflask extension l3. These various parts will now be described in detail.

In the form of the invention shown, the flask Ill consists of anordinary casting ring-cylindrical in form which is of proper height anddimensions to receive the pattern and allowfor suffi- 1 cient space toinvest the pattern within said flask.

' withstanding the temperature brought about by pouring the moltencasting material into the mold. Although I have shown the flask It! asbe- "ing cylindrical it can readily be comprehended that the same may beconstructed with any suitable form, as for example to fit the particulararticle desired to be cast in the same. v

The base II is constructed of rubber or some other similar suitableresilient material and is circular in form, being provided at itsperiphery with an,upwardly extending annular gripping member H adaptedto extend about and receive the lower end l8 of the flask III. Therubber from which the base H is constructed is preferably of su ch anature that the member I! has suflicientfriction to hold the basesecurely attached to the flask It. At the center of the base II isprovided a protuberance H! which extends upwardly into sprue enlargement2! in which the molten casting material inserted and by which the sameis directed in o the mold cavity. This protuberance has at the highestpoint of thesame formed in it a vertically extending hole 22 which isadapted toreceive and support a sprue pin 23. The wax pattern isindicated at 24 and is mounted upon the sprue pin 23, as clearly shownin Fig. 2.

The flask extension l3 has been shown in the drawings as a duplicate oftheflask Ill. This flask extension is cylindrical in form, being open atits ends, as designated at 25, and forms. an

/ebullition chamber 26 communicating with the interior of the flask II)when superimposing the same. This flask extension is formed withsharpened edges 21 which serve the same purpose as the sharpened edgesl4 of the flask II). It can readily be comprehended, however, that theflask extension I3 can be constructed of any desired shape and size,although with my invention an' extra flask which is always available inthe casting room may be used to form this extension. Inasmuch as theflask extension l3 is'n'ot sub- :Iected to temperatures above roomtemperature, the same may be constructed of any desired material;

The flask extension I3 is held attached to the flask M by means of thecoupling l2. This coupling is constructed of any suitable flexiblematerial having suflicient friction to hold the parts in place and ifdesired may be constructed of rubber or the same material as the basell.

The said coupling comprises a positioning flange 28 which is adapted tobe disposed between the juxtaposed sharpened edges 21 and I4 ofthe'flask extension'l3 and the flask ill and forms a seal between thesetwo parts preventing leakage of investment from between the same. Thecoupling 12 has an annular grip issuing upwardly from the positioningflange v23 of the same material as said flange, which grip is adapted toenparatus' is prevented. After the parts have been circle the lower end3| of the flask extension I3 to hold the same rigidly attached thereto.Coupling 12 has another similar annular grip 32 issuing downwardly fromflange 28 which is adapted to encircle the upper portion 33 of the flaskID to hold the said coupling securely attached to the flask. Thepositioning flange 28, in addition to forming a seal between the ends ofthe flask and flask extension, also serves to v position the couplingwith relation to the ends of the flask and flask extention so that thetwo' ends thereof project similar distances into the coupling. By meansof this construction the coupling .is rigidly secured to the two partswith the parts in proper relation to one another. The internal diameterof the flange 28 is substantially equal to the internal diameter of theflask I I and also that of the flask extension l3 which may be the sameas thatof said flask. In this manner the inner surfaces of the flaskextension I! and the flask Ill lie substantially in continuation of oneanother.

In the use of my invention I employ evacuating apparatus which consistsof a table 34 supported upon feet 35. Thistable has a smooth top 33 andhas connected to it an air outlet 32 which in turn is connected to ahose or tube 38 leading to a suitable vacuum pump or any suitableevacuating chamber. The said apparatus further includes a bell jar 39,having a cylindrical wall 4l, a=top 42 and a knob 43 secured to saidtop. The lower 'edge 44' of the wall 4l is ground to form an air-tightseal between said bell jar and the table 34 so that, when the said bell.iar is placed upon the table in a manner to enclose the air outlet 3'5,an evacuating chamber 45 is provided. g

The method of using the invention is as follows: The sprue pin 23 isfirst inserted into the hole 22 in .the base I! and the wax patternattached to the same in any suitable manner. The said sprue pin is ofsuch length and dimensions as to, support the pattern in spaced relationto the walls of the flask l0 when the same is applied to the base. FlaskIi! is next placed over the pattern and the lowermost end 18 thereof.inserted into the annular grip ll of the base. until the sharpened edgeId of said flask engages the upper surface of the base I i. when soapplying the flask to the base the grip ll hugs the lower end it of theflask and holds the base rigidly attached to the flask." The coupling 12is next applied to the upper end 33 of the flask It by forcing the grip32 over the end of the same and moving the said coupling downwardly.This procedure continues until the sharpened edge l4 of the flask 10engages the underside of the flange 2B. The flask extension I3 is nowapplied to the upper end of the coupling l2 by inserting the lower end3! thereof into the annular grip 29' until the sharpened edge 2'! ofsaid flask extension engages the upper surtace of the flang 28. Bypressing downwardly upon the assembled. structure-both the sharpenededge 14 and the sharpened edge 21 are caused to form a seat against theflange 28 whereby leakage of investment out of the molding apassembled,as designated. a sufficient quantity of investment in plastic form isinserted into the flask l0 through the open end of the flask extensionl3. An amount suflicient to fill the flask Ill may be employed or alesser amount may be used if less investment is required to completelyinvest the pattern within the same. The molding apparatus is then setupon the table 34 and the bell jar 39 placed over the same and caused torest upon the said table to bring the ground edge 44 thereof in contactwith the surface 36 of said table. The chamber 45 within the bell jar 39is then evacuated through the .air outlet 31 and the tube 38. Suchevacuation produces ebullition within the ebullition chamber 36 wherebyall of the air trapped in the investment is withdrawn therefrom. Thechamber 45 is preferably subjected to vacuum during a period continuingthroughout the ebullition within chamber 26. Thereupon the vacuum is cutoff and the bell Jar'39 removed to give access to the molding apparatus.During ebullition the investment bubbles up into the ebullition chamber26, and upon termination of ebullition settles back into the flask ID tocompletely invest. the pattern.-- In Fig. 2 the investment is shown asreaching up to the top of the flask l0 and is indicated by the referencenumeral 46. At this stage the flask extension l3, the coupling l2 andthe base II are all removed from the flask Ill. The relation of theparts with the flask extension and coupling removed is shown inFig. 3.Thereafter the sprue pin 23 is withdrawn from the investment. Uponapplying heat to the mold comprising the flask In, the investment 46 andthe pattern 24. the

pattern is melted a d flows out of the mold to able size and shape.Withdrawal of the sprue pin from the mold provides the sprue 49 and thesprue enlargement 2| being formed by the protuberance 19 of base H. Themold ascompleted is shown/in Fig. 4 and is ready to receive the moltencasting material.

Theadvantages of my invention are apparent.

By evacuation, the air within the investment is completely withdrawn sothat airbubbles are prevented from forming at the surface of the moldcavity whereby extremely smooth and perf ect castings result. By the useof the base with ,the flexible annular grip the lower end of the 1 moldis readily and easily closed. By means of the flask extension standardflasks such as are readily found in the casting room may be employedwithout alteration. The coupling used serves to,connect the flaskextension to the flask which functions only during the ebullition of theI investment and which may 'be easily removed after setting of theinvestment to permit of continuing with the elimination of the wax fromthe mold cavity and the casting of the molten casting material. Theflange formed in the coupling serves to position the juxtaposed ends ofthe flask and flask extension within the coupling so that each partextends the required distapce into the couplingand in addition forms aseal between two ends of the flask and flask extension preventingleakage of the investment out of the flask. Due'to the fact that theflask extension-is of the same dimensions a the flask the inner surfacethereof lies in continuation of the inner surface of the flask wherebythe investment in the ebullitionfchamber readily returns into the flaskupon cessation of ebullition and with a minimum danger of adhering tothe walls of the flask extension. By employing a bell jar for forming anevacuation chamber the upper end of the flask extension'may be left opento permit of pouring the investment into the flask through the open endthereof, thus greatly simplifying the method of investing the pattern.

With my improved method the teps are exceedingly simple and practicaland result in considerable economy in time and in addition producecastings of smooth surface andwithcut flaws.

Changes in the specific form of my invention, as herein disclosed, maybe made within the scope of what is claimed without departing from thespirit of my invention.

Having described my invention, what I claim as new and desire to protectby Letters Patent is:

l. Molding apparatus for investing patterns .under vacuum comprising aflask open at its ends, and adapted to receive a quantity of inandforming an ebullitionchamber communicating with said flask, and acoupling having a part forming a seat for engagement with the edges ofsaid flask and flask extension to form a seal therebetween.

3. Molding apparatu for investing patterns under vacuum comprising aflask open' at its ends, a base attached to said flask and closing thelower end thereof, means for supporting the pattern and forming a sprueleading to the mold cavity, a flask extension superimposing said flaskand forming an ebullition chamber communicating with said flask, acoupling having two flexible frictiomgrip for engagement with thejuxtaposed ends of said flask and flask extension for connecting themtogether, and positioning means within the coupling for engagement with.the edges of said flask and flask extension for procuring properengagement of the grips with said flask and flask extension.

4. Molding apparatus for investing patterns under vacuum comprising aflask open at its ends, a base attached to said flask and closingresilient material and holding said parts in proper relation, andpositioning means within .the coupling for engagement with the edges ofsaid flask and flask extension for procuring proper engagement of thegrips with said flask and flask extension.

5. Molding apparatus for investing patterns. 'under vacuum comprising aflask open at its ends, a base on which said flask is adapted to restfor closing the lower end thereof, an annular grip formed on said baseand constructed of flexible resilient material for embracing the lowerend of said flask upon the exterior thereof and holding the baseattached thereto, and means carried by the base for supporting thepattern and forming a sprue leading to the mold cavity.

'6. Molding apparatus for investing patterns under vacuum comprising aflask open at its vestment sufficient to invest the pattern; a base Hattached to said flask and closing the lower end thereof, means carriedby the base for supporting the pattern and forming a sprue leading tothe mold cavi y a flask extension su erimposing said flask and open atits ends, said flask extension forming an ebullition chambercommunicating with said flask, and having a capacity suflicient toreceive a portion of the contents of the flask during ebullition, and acoupling connecting said extension to said flask. 2. Molding apparatusfor investing patterns under vacuum comprising a fla'sk open at itsends, a base attached to said flask-and closing the lower end thereof,means for supporting the pattern and forming a sprue leading to the moldcavity", a flask extension superimposing said flask ends, a base onwhich said flask is adapted to rest for closing the lower id thereof, anannular grip formed on said base and constructed of flexible resilientmaterial for embracing the lower end of said flask and holding the baseattached thereto, means for supporting the pattern and forming a sprueleading to the mold cavity, a flexible coupling having two annularfriction grips for engagement with the juxtaposed ends of said flask andflask extension, said friction, grips being constructed of flexibleresilient material and connecting said parts, and positioning meanswithin thecoupling for engagement with the edges of said flask and flaskextension for holding said flask and flask extension in proper relationwith respect to one another andto said grips.

'7. Molding apparatus for investing patterns.

flask and forming an ebullit ion chamber conimunicating with said first.named flask, and a coupling encircling said flasks upon the exteriorthereof and connecting said flasks together in a manner to producesubstantial continuity between the surfaces of said flasks. d

8. Molding apparatus for investing patterns under vacuum comprising acasting ring open at its ends, a base attached to said casting ring andclosing the lower end thereof, means for supporting the pattern andforming a sprue leadrings properly mounted in said coupling and suitablypositioned relative to one another.

9. Molding apparatus for investing patterns under vacuum comprising acasting ring open at its ends, a base attached to said casting ring andclosing the lower end thereof, means for supporting the pattern andforming a sprue leading t o the mold cavity, a second casting ring ofthe same diameter .as said first named casting ring and open at itsends, said second named casting ring superimposing said first namedcasting ring and forming an ebullition chamber communicating with saidfirst named casting ring, and an annular coupling encircling thejuxtaposed ends 01 said casting-rings and having a positioning flangeintermediate its ends adapted to engage the edges of said casting ringsfor holdingthe casting rings properly mounted in said coupling andsuitably positioned relative to one another, the internal diameter ofsaid flange beextension, in placing the entire mold assembly into achamber, in exhausting the air from the chamber for a period continuingduring ebullition o! the. investment within said flask extension and inremoving said flask, extension coupling and base from said flask.

11. The method of investing patterns under vacuum which consists inattaching a base to a casting ring open at its ends in a manner toclose'the lower end thereof, in supporting the pattern within thecasting ring, in applying an annular coupling to the exterior of saidcasting ring at the upper end thereof, in inserting the lower end of asecond casting ring into said coupling in a manner to form an ebullitionchamber communicating with the interior of said first named casting ringin placing the entire mold assembly'intc a chamber, in exhausting theair from the chamber for a period continuing during ebullition of theinvestment within said ebullition chamber and in removing said secondingsubstantially equal to the internal diameter of said casting rings tomake the inner surfaces of said casting rings lie substantially incontinuity relative to one another.

10. The method oi investing patterns under vacuum which consists inattaching a base to the lowerend of a flask in a manner to close thesame, in supporting the pattern from the named casting ring, couplingand base from said first named coupling ring. T

12, Molding apparatus for investing patterns under vacuum comprising aflask open at its ends, a base attached to said flask and closing thelower end thereof, means carried by the base for supporting the patternand forming a sprue leading to the mold cavity, a second flask open atits end and superimposing said first named flask and forming anebullition chamber communicating with said first named flask, and meanshavinga chamber under vacuum communicating with the upper end of thesecond flask.

13. Molding apparatus for investing'patterns under vacuum'comprising aflask open at its ends, a'base attached to said flask and closing thelower end thereof, meanscarried by the base for supporting the patternand forming a sprue leading to the mold cavity, a flask extensionsuperimposing said flask and means having a chamber under vacuumcommunicating with'the upper end oi said flask extension.

14. Molding apparatus for investingv patterns under vacuum comprising aflask open at its ends, a base on which said flask isadapted to rest forclosing the lower end theroef, an annular base, in applying aflaskextension open at its ends to the upper'end of the flask by meansof a coupling in a manner to'communicate with the interior of the flask,in pouring into the flask through the open end of the flask extensionsufflcient investment to invest the pattern and less than the combinedvolume of the flash and flash flange formed on said base and constructedof flexible resilient material, said flange embracing the lower end ofthe flask upon the exterior thereof and means carried by the base forsupporting the pattern and forming a sprue leading to the mold cavity.

CHARLES HAROLD BRACE.

